Limiting the temperature for comfort and energy conservation by means of a space or room thermostat has been done for many years. In thermostats making use of separate adjusting levers for heating and for cooling operation, the limiting action is quite simple in that a stop is used for the heating lever and a stop is used for the cooling lever, and these stops can be independently set at a fixed position.
In thermostats where a single control point adjusting knob is used, such as in the Carl G. Kronmiller U.S. Pat. No. 2,729,719, issued Jan. 3, 1956, which may have a subbase for switching the thermostat between heating and cooling apparatus such as in the Walter E. Edelman U.S. Pat. No. Re. 28,676, issued Jan. 13, 1976, the single control point adjustment means must have stops that are only used in either the heating or cooling operation. One particular thermostat for accomplishing such a limiting action is disclosed in the Donald P. Kolbow U.S. Pat. No. 4,078,601, issued Mar. 14, 1978. The Kolbow thermostat has a single control point adjustment knob with separate ranges for heating and cooling operation. Such a thermostat has the disadvantage that the control point adjustment knob can be inadvertently placed in the OFF position, and the homeowner would not be aware that his system was completely off. Another thermostat disclosed in the Richard E. Fitzgerald, et al., U.S. Pat. No. 4,249,155, issued Feb. 3, 1981, has a single control point adjustment knob with a changeover lever for switching the thermostat between heating and cooling apparatus. The limit means includes a separate cooling button or heating button which must be operated with the changeover lever to accomplish the limiting action. Such a thermostat is complicated to operate and requires more parts increasing its production cost.
The present invention is concerned with a thermostat having a single lever changeover switch means which selects the limiting action of the thermostat depending upon whether the single control point adjustment knob is to be used in the heating or cooling range of operation. During the heating operation, a first range of operation is selected, and during the cooling operation, a second range of operation is selected. With such an invention, when the single lever is moved to provide a heating mode of operation, a maximum temperature such as 72.degree. F. is provided, and when the single lever is moved to the cooling mode of operation, a minimum temperature such as 78.degree. F. for cooling is provided.